Re: [HACKERS] high shared buffer and swap

From: PFC <lists(at)peufeu(dot)com>
To: "Laurent Laborde" <kerdezixe(at)gmail(dot)com>, pgsql-performance(at)postgresql(dot)org
Subject: Re: [HACKERS] high shared buffer and swap
Date: 2009-05-05 09:15:51
Message-ID: op.utf9cpn7cigqcu@soyouz
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> An octocore server with 32GB of ram, running postgresql 8.3.6
> Running only postgresql, slony-I and pgbouncer.
>
> Just for testing purpose, i tried a setting with 26GB of shared_buffer.
>
> I quickly noticed that the performances wasn't very good and the
> server started to swap slowly but surely.
> (but still up to 2000query/second as reported by pgfouine)
>
> It used all the 2GB of swap.
> I removed the server from production, added 10GB of swap and left it
> for the weekend with only slony and postgresql up to keep it in sync
> with the master database.
>
> This morning i found that the whole 12GB of swap were used :

Hm, do you really need swap with 32Gb of RAM ?

One could argue "yes but swap is useful to avoid out of memory errors".
But if a loaded server starts to swap a lot, it is as good as dead
anyway...

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